Sunday, November 4, 2012

Silver vs. Marcels

Another interesting look at Nate Silver's work - great when it works, but hard to duplicate. Unless you monkey with the data.For most players in most years, Silver’s PECOTA worked pretty well. But the world of baseball research, like the world of political psephology, does have its cranky internet termites. They pointed out that PECOTA seemed to blunder when presented with unique players who lack historical comparators, particularly singles-hitting Japanese weirdo Ichiro Suzuki. More importantly, PECOTA produced reasonable predictions, but they were only marginally better than those generated by extremely simple models anyone could build. The baseball analyst known as “Tom Tango” (a mystery man I once profiled for Maclean’s, if you can call it a profile) created a baseline for projection systems that he named the “Marcels” after the monkey on the TV show Friends—the idea being that you must beat the Marcels, year-in and year-out, to prove you actually know more than a monkey. PECOTA didn’t offer much of an upgrade on the Marcels—sometimes none at all.